Introducing the highlights (13 geosites) of the West Izu area

The highlights of the West Izu area
On the cliffs of Dogashima coast, you can see a submerged debris flow associated with the eruption of a submarine volcano, and pumice and volcanic ash layers deposited on it.
The white and beautiful striped strata create the characteristic scenery of Dogashima.
On the cliffs of the shore, there is Tensodo, a sea cave eroded by waves and the ceiling fell down, that can be enjoyed from the promenade and pleasure boats.
Muroiwa cave is a trace of a stone quarry where "Izu stone", which is a solidified volcanic ash erupted from a submarine volcano, was quarried until the early Showa era.
It was renovated for sightseeing, and you can observe the strata inside the tunnel-shaped stone quarry while feeling a little thrill. The traces of various ingenuity of craftsmen when quarrying by hand are also highlights.
Mount Eboshi is a volcanic neck 162 meters above sea level. It is impressive that Mt. Eboshi is rising from the sea.
There is a stone staircase leading from the foot to the summit where the shrine is located, and from the summit you can enjoy a superb view of the southwest coast of Izu, Mount Fuji and Suruga bay.
Bentenjima once was a small island where fishermen crossed by boat. The island was connected to the land during construction of the river mouth in 1967.
A small shrine sits on top of the 99 stone steps.
On the promenade around the island, you can see the lava strata that flowed to the seabed when Izu was in the southern sea.
The island is full of special trees that are used to make charcoal.
Toi Gold Mine
The high geothermal heat generated by volcanoes have created various ores in Izu. Gold mines are one of them, and gold had been mined in various parts of Izu.
Toi Kinzan is a sightseeing mine where a part of the former tunnel was preserved and maintained, and a museum was added. In the Edo and Meiji eras, it boasted the second largest production after Sado Gold Mine, producing 40 tons of gold and 400 tons of silver.
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Under the volcano, there is a magma path through which magma passes from deep underground. The path of this magma that emerges on the surface of the earth when it rises due to crustal deformation is called "volcanic neck".
Senganmon is a part of this “volcanic neck”, and the bottom of Senganmon was eroded forming the “gate” in the center of a huge rock.
Mihama Cape
Cape Mihama, like a bird's beak, is a terrain called a sand spit that is made up of a band of sand that has been carried into the currents of Suruga Bay at the entrance of the bay. Suruga Bay, which extends outside Heda Port, is the deepest bay in Japan and is home to a wide variety of marine life.
Heda Port, which is surrounded by Cape Mihama, is a good natural port where spider crabs and deep-sea fish are caught.
Koganezaki Cape
Rocks are altered by hot spring water under the geothermal field created by volcanoes. The color of the rocks of Koganezaki, which shines golden in the sunset, was also dyed by such alteration.
It is one of the sunset spots in Nishi-Izu Town. Mount Fuji and the ridge of West Amagi mountains can be seen from the observation deck where Suruga Bay spreads.
Isiki Pillow Lava
This is the oldest stratum in the Izu Peninsula, consisting mostly of lava and submarine debris flows that have flowed off during submarine eruptions. Pillow lava is part of the oldest lava flow in this stratum. When less viscous lava flows to the bottom of the water, it forms like a pillow due to surface tension and rapid cooling. Here, you can observe the cross section of the stacked pillow lava.
Sanshiro Island & Tombolo
The islands are called Sanshiro Islands because three or four islands can be seen depending on the viewing angle. The islands are trajectory of the path of the magma that were once under the submarine volcano. Stones and rocks accumulated between Sanshiro Islands and the land, forming the shallows.
At low tide, you can walk from the coast to Sanshiro Islands on the other side. This phenomenon is called "Tombolo” in Italy.
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Futo Coast
You can observe group of the dikes that supplied magma to the former submarine volcano. The magma, which rose several times, created many dikes underground. These dikes under the ground rose due to the collision between Izu and Honshu. Later, the soft strata around the dikes were eroded, and hard dikes appeared on the ground like dorsal fins.
Ishibu Rice Terraces
Number of small rice terraces are maintained at the foot of the Jaishi volcano that erupted about 1.4 million years ago. Abundant springs and groundwater from volcanoes caused landslides, creating gentle slopes used as rice terraces. Although the terraced rice fields were temporarily unused, preservation activities have maintained the beautiful terraced rice fields so that they can be selected as one of the top ten rice terraces in Shizuoka Prefecture.
Sawada Park & Karano Park
You can see the submarine debris flow accompanying the eruption of the submarine volcano, and the scenery created by pumice and volcanic ash layers piled up on the sea floor. Sawada Park also has an open-air bath with a panoramic view of Dogashima.
Submarine debris flows associated with the eruption of submarine volcanoes, and crushed lava flowing out to the sea floor can be seen. The stratum of volcanic ash deposited on the sea floor has a serpentine undulating pattern. Because submarine volcanic erupted at the bottom of the sea, we cannot see. The formation was raised without much disturbance, so you can see and touch the situation at the time of the eruption.